The aim of this study was to determine effect of in ovo injection of nanoparticles of zinc oxide on hatching, growth performance and carcass yield of broiler chicks after hatching. In total, 324 fresh hatching eggs were randomly distributed into six treatment groups of 54 eggs per treatment with three replicates of 18 eggs each, and injections were performed on day 15 of incubation. The treatments were sham, positive control injection of 60 ml of distilled water and in ovo injection 4 levels (15, 30, 60 and 120 ppm) of zinc oxide nanoparticles into site of the embryo in amniotic fluid sac. The results showed that in ovo injection of nano zinc oxide did not affect chicks feed intake in total rearing period (P>0.05). Also, there were no significant inovo injection different levels of zinc oxide nanoparticles on body weight, and average daily gain and feed conversion ratio in the three periods, 1-10, 11- 42 days and total rearing period among treatments. Inovo injection of 15, 30 and 60 ppm of nano- zinc oxide did not affect the percentage of hatching compared to the control group. While the injection of 120 ppm in fertile eggs reduced the percentage of chicken intake compared to the control group, positive and negative (P <0.05). The results showed that in-ovo injection of 15, 30 and 120 ppm nano zinc oxide did not have a significant effect on the weight of hatched chicks compared to control group. However, The results showed that groups receiving levels 60 ppm zinc oxide nanoparticles had significant increase on body weight of the hatched chicks compared with the positive control group (P <0.05). In-ovo injection of different levels of nano- zinc oxide had no effect on carcass weight, heart weight, bursa of fabricius weight and spleen weight. The results of this study suggest that in-ovo injection zinc oxide nanoparticles on day 15 of incubation fertilized eggs could not improve feed intake, feed conversion ratio, hatching percentage and carcass yield of broiler chickens.